2-Deoxy-2-[18F]fluoro-d-glucose-Positron Emission Tomography and Positron Emission Tomography/Computed Tomography Diagnosis of Patients with Recurrent Papillary Thyroid Cancer

Abstract

2-Deoxy-2-[F-18]fluoro-D-glucose positron emission tomography (FDG-PET) has an established role in restaging of various cancers, including papillary and undifferentiated thyroid carcinoma, but detection rates are variable in the published literature. We were therefore prompted to review our experience with FDG-PET in detection of recurrent papillary thyroid cancer (PTC). This is a retrospective study (April 1, 1995-March 31, 2005) of 21 patients with histologic diagnosis of PTC who had PET examinations. The group included seven men and 14 women, with age range of 26-75 years (average 50 +/- 16). The PET scan request was triggered by rising levels of thyroglobulin (Tg) in the presence of a negative iodine-131 scan. Recurrent/metastatic disease was identified by PET in 16 (76%) of the 21 patients with PTC. The sensitivity and specificity of FDG-PET for disease detection in this cohort were 88.2% [95% confidence interval (CI), 65.7-96.7] and 75% (95% CI, 30.1-95.4), respectively. The Tg levels were 1.0-10.4 ng/ml (average, 4.52 ng/ml) in the patients with negative PET scans and 1.0-38 ng/ml (average, 16.8 ng/ml) in patients with positive scans. The lesions were located in the cervical lymph nodes (8), thyroid bed (4), lungs (4), and mediastinal lymph nodes (2). Our study confirms the feasibility of PET in detection of residual/recurrence of PTC, with sensitivity of 88.2% (95% CI, 65.7-96.7) and specificity of 75% (95% CI, 30.1-95.4). Detectable levels of Tg, even in the presence of negative I-131 scan or anatomic imaging, should prompt restaging with FDG-PET.